The 4 output ports of the ADAU1452 are connected to the codec AD1938. Is it possible to use the outputs in their digital form (before the 1938) ?
The 4 serial port pins (SDATA_OUTx, BCLK_OUTx and LCLK_OUTx) which are connected to the AD1938 are also exposed on test points between the 2 chips. You should be able to tap these signals and connect to other external serial audio I2S or TDM inputs.
Also note per the EVAL-ADAU1452MINIZ user's guide: "When connecting these signals to external devices, at least one ground signal should be connected as well, in order to maintain signal integrity."
This is what I hoped but wondered if the connexion already existing with the codec would interfere in any way with a parallel connexion to the I²S input of a FDA amplifier.
As long as the off-board connections are as short as possible, you should be fine. It looks like the eval board includes 33 ohm series/source terminating resistor block (R5) right between the DSP and the test points for all of the ADAU1452 serial port output pins which are connected to the AD1938 codec.
If the data format is the same as the default/standalone (48 kHz, 24-bit I2S) format for the AD1938, I would imagine the audio could play simultaneously out of both devices. If you do modify the ADAU1452 default serial port configuration within SigmaStudio for your connected device, I do not see any bus contention resulting between the AD1938 and other device, but most likely the AD1938 would play back noise or nothing at all on it's stereo output connectors when you change the sample rate and serial mode.
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